A Python CSV splitter

csv_splitter.py

import os

def split(filehandler, delimiter=',', row_limit=10000, 
    output_name_template='output_%s.csv', output_path='.', keep_headers=True):
    """
    Splits a CSV file into multiple pieces.
    
    A quick bastardization of the Python CSV library.

    Arguments:

        `row_limit`: The number of rows you want in each output file. 10,000 by default.
        `output_name_template`: A %s-style template for the numbered output files.
        `output_path`: Where to stick the output files.
        `keep_headers`: Whether or not to print the headers in each output file.

    Example usage:
    
        >> from toolbox import csv_splitter;
        >> csv_splitter.split(open('/home/ben/input.csv', 'r'));
    
    """
    import csv
    reader = csv.reader(filehandler, delimiter=delimiter)
    current_piece = 1
    current_out_path = os.path.join(
         output_path,
         output_name_template  % current_piece
    )
    current_out_writer = csv.writer(open(current_out_path, 'w'), delimiter=delimiter)
    current_limit = row_limit
    if keep_headers:
        headers = reader.next()
        current_out_writer.writerow(headers)
    for i, row in enumerate(reader):
        if i + 1 > current_limit:
            current_piece += 1
            current_limit = row_limit * current_piece
            current_out_path = os.path.join(
               output_path,
               output_name_template  % current_piece
            )
            current_out_writer = csv.writer(open(current_out_path, 'w'), delimiter=delimiter)
            if keep_headers:
                current_out_writer.writerow(headers)
        current_out_writer.writerow(row)

got a armap' codec can't decode byte 0x81 in position 6696: character maps to . Whats wrong

On Unix-like systems, and if you don't need to include the headers in each file, you can use the built-in split command.

split won't work if your data has quoted cells with newlines in them.

Thanks for the starting point! Was able to make a single file CSV split by column program after looking at your code. https://github.com/APAHRoot/HelpfulHopeful

Hopefully it works for other people too!

Thanks for posting this. Very useful. Why do I get a "NameError: name 'current_out_writer' is not defined"

Thank you for this. Works like a charm. For thoose of you who have trouble using this ;

1. You need to set your row limit for your own data size
2. If you are using python 3.x , you need to change the line "headers=headers.next() " into "headers=next(headers)"
3. You need to change the output_path to a folder where the splitted data files to be stored.

I wonder if it is easy to make each file have unique dates. For instance, I want 1st May of 2019 lines to be in one file only.

I wonder if it is easy to make each file have unique dates. For instance, I want 1st May of 2019 lines to be in one file only.

Should be able to do that with this: https://github.com/APAHRoot/HelpfulHopeful/blob/master/SortBySplitCSV.py

I made it to split data by county, but it should work with any value you want to use as an identifier

I wonder if it is easy to make each file have unique dates. For instance, I want 1st May of 2019 lines to be in one file only.

Should be able to do that with this: https://github.com/APAHRoot/HelpfulHopeful/blob/master/SortBySplitCSV.py

I made it to split data by county, but it should work with any value you want to use as an identifier

I am testing it now. I guess the column name has to be added instead of the "Unnamed". The code doesn't have a row or mb limit. The split by date will help. Hopefully, I can edit that and add a date range (per month etc).

HI <

I am new to Python and it is not working. Can some one please help I am using Python 3.5.
From what is see it is not going into the loop, "for i, row in enumerate(reader):"
The output of the print(next(reader)) statement is ['d'] , looks like it is taking the 1st character of the file path.
One more thing i csaw is that the out put file that is created called "cat output_1.csv" contains the complete path of the CSV file that needs to be broken into multiple CSV files.
cat output_1.csv
a
t
a
/
t
r
a
n
s
f
o
r
m
a
t
i
o
n
s
/
t
e
m
p
_
s
m
a
l
l
.
c
s
v

The csv file has 10K rows.
The code is as follows.
The call to the function is as follows.
csv_splitter.split("data/transformations/temp_small.csv", ',',row_limit=10000,
output_name_template='output_%s.csv', output_path='.', keep_headers=True)

The function is
import os

def split(filehandler, delimiter=',', row_limit=10000,
output_name_template='output_%s.csv', output_path='.', keep_headers=True):
"""
Splits a CSV file into multiple pieces.

A quick bastardization of the Python CSV library.
Arguments:
    `row_limit`: The number of rows you want in each output file. 10,000 by default.
    `output_name_template`: A %s-style template for the numbered output files.
    `output_path`: Where to stick the output files.
    `keep_headers`: Whether or not to print the headers in each output file.
Example usage:

    >> from toolbox import csv_splitter;
    >> csv_splitter.split(open('/home/ben/input.csv', 'r'));

"""
import csv
reader = csv.reader(filehandler, delimiter=delimiter)
current_piece = 1
current_out_path = os.path.join(
    output_path,
    output_name_template % current_piece
)
print("The current output path" + current_out_path)
print("The file name is " + filehandler)

current_out_writer = csv.writer(open(current_out_path, 'w'), delimiter=delimiter)
print("current_out_writer is " )
print(current_out_writer)
print(next(reader))
current_limit = row_limit
if keep_headers:
    #headers = next(reader)
    headers=next(headers)
    current_out_writer.writerow(headers)
for i, row in enumerate(reader):
    if i + 1 > current_limit:
        print("In the function csv_splitter")
        current_piece += 1
        current_limit = row_limit * current_piece
        current_out_path = os.path.join(
            output_path,
            output_name_template % current_piece
        )
        current_out_writer = csv.writer(open(current_out_path, 'w'), delimiter=delimiter)
        if keep_headers:
            current_out_writer.writerow(headers)
    current_out_writer.writerow(row)

after fixing "headers=headers.next() " I had this error
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 5376: character maps to <undefined>
anyone can help me?
many thanks

encoding='utf-8', add it as parameter

open(current_out_path, 'w',encoding='utf-8') for example. @hoai97nam

Adding a working solution, python3 and with encoding.

`import os

def split(filehandler, delimiter=',', row_limit=8500,
output_name_template='output_%s.csv', output_path='.', keep_headers=True):
"""
Splits a CSV file into multiple pieces.

A quick bastardization of the Python CSV library.

Arguments:

    `row_limit`: The number of rows you want in each output file. 10,000 by default.
    `output_name_template`: A %s-style template for the numbered output files.
    `output_path`: Where to stick the output files.
    `keep_headers`: Whether or not to print the headers in each output file.

Example usage:

    >> from toolbox import csv_splitter;
    >> csv_splitter.split(open('/home/ben/input.csv', 'r'));

"""
import csv
reader = csv.reader(filehandler, delimiter=delimiter)
current_piece = 1
current_out_path = os.path.join(
    output_path,
    output_name_template % current_piece
)
current_out_writer = csv.writer(open(current_out_path, 'w',encoding='utf-8'), delimiter=delimiter)
current_limit = row_limit
if keep_headers:
    headers = next(reader)
    current_out_writer.writerow(headers)
for i, row in enumerate(reader):
    if i + 1 > current_limit:
        current_piece += 1
        current_limit = row_limit * current_piece
        current_out_path = os.path.join(
            output_path,
            output_name_template % current_piece
        )
        current_out_writer = csv.writer(open(current_out_path, 'w',encoding='utf-8'), delimiter=delimiter)
        if keep_headers:
            current_out_writer.writerow(headers)
    current_out_writer.writerow(row)

split(open('test.csv','r',encoding='utf-8'))`

Thanks for the starting point! Was able to make a single file CSV split by column program after looking at your code. https://github.com/APAHRoot/HelpfulHopeful

Hopefully it works for other people too!

This is amazing and is exactly what I was looking for. Thank you so much.

Thanks for the starting point! Was able to make a single file CSV split by column program after looking at your code. https://github.com/APAHRoot/HelpfulHopeful
Hopefully it works for other people too!

This is amazing and is exactly what I was looking for. Thank you so much.

@alternateaccounts You can test this tool with your 4.5gb file?

https://github.com/BurntSushi/xsv

Thank you by the mention in your project

I am sorry about this, I am new to the field, but where I should specify the file I want to split into smaller files? at which part of the code?

https://pypi.org/project/filesplit/

add newline=‘’ in open() to avoid blank row